The
Black-vented Shearwater is a species of the eastern Pacific, nesting on
islands off of western Baja California, with non-breeding birds spread
across the eastern Pacific from California southward to coastal Mexico.
While a pelagic species, they come closer to shore than many shearwaters and
in range are commonly seen on pelagic bird tours. They are named for the
dark undertail coverts, a feature that distinguishes them from other
shearwater species that have light-colored undertail coverts.

Habitat: The few islands on which Black-vented
Shearwaters breed are generally dry with either barren sandy soil in which
nesting burrows are built, or with deep rocky crevices that serve as nesting
sites. Pelagic outside of the breeding season, although they are often
found relatively close to shore.

Diet: Feeds on small fish, squid, and crustaceans.

Behavior: Black-vented Shearwaters feed by
plunging into the water while in flight, or by making dives from a floated
position on the water. They will also feed from flight, dipping down
and skimming prey items at or near the surface. They are mostly nocturnal
around their breeding colonies.

Nesting: Black-vented Shearwaters are colonial
nesters, returning each year to traditional nesting sites on Islas San
Benito, Islas Natividad, and Isla de Guadalupe off the coast of western Baja
California. The nest is a burrow built in sandy soil, or a deep rocky
crevice. A single egg is laid, with both parents helping to incubate
the egg. The incubation period is approximately 50 days, with both
parents helping to raise the young. Young fledge after about 70 days.

Song: On breeding colonies, nighttime calls
similar to haunting wails are heard. They are usually silent away from
breeding sites.

Migration: Breeds in a select number of islands
off the coast of Baja California. Movements outside of the breeding
season are erratic. They can be found off the coast of southern California
in any season, but become more numerous in the fall and winter. Other
movements are poorly understood. Water temperature may play a key role in
non-breeding bird movements, with birds following sea surface temperatures
that are suitable for their preferred prey items.

Similar Species:
Once considered a subspecies of the Manx
Shearwater, that is the species it is most likely to be confused with
visually, but the Manx Shearwater is a bird of the Atlantic Ocean.
Also similar to Audubon's Shearwater,
but that species too is found in the Atlantic and not the Pacific.

Conservation Status: Introduced predators on
breeding islands, particularly rats and cats, have directly influenced
nesting success and overall populations. Overall populations strongly
declined from historical levels, but eradication of cats from its primary
breeding island, Natividad, have resulted in a stabilization of populations.
Cats, dogs, rats, and other predators continue to be a threat on other
breeding islands, and as a result, up to 90% of the world's population
breeds on Natividad. Given the small breeding range, continued threats
from introduced predators, and that the population is so reliant on one
breeding site,
the IUCN has listed the Black-vented Shearwater as "near threatened".